On 2019/2/25 13:28, Jiaxun Yang wrote:
2019年2月24日 下午5:36于 kernel@xxxxxxxxxx写道：
From: Wang Xuerui <wangxuerui@xxxxxxxxx>
Hi,
This is my WIP patchset to add support for using the on-chip ExtCC
(external counter) register as clocksource, to boost the real-time
performance on Loongson platform. I'm posting this to solicit comments
and get some of the unresolved questions answered.
Hi Xuerui
Thanks a lot for your works, however, the ExtCC can be influenced by the frequency of CPU core, and we have cpufreq working on Loongson-3 processors, so you should mark it conflict with cpufreq driver.
And as far as I know, ExtCC is even not synchronous between different cores.
I'd prefer to use gs3_HPT(0x3ff00408) register to implement this feather. Also it can be accessed from all the nodes, and the clock comes from "node clock" which will not effected by core frequency.
This is interesting, but according to Section 2.4.3 of the 3A3000 User
Manual (Vol. 2), the ExtCC register is explicitly stated to be
core-frequency-independent.
Maybe you confused ExtCC with Count (rdhwr with rd=2), of which update
freq does vary with core freq?
